When iron reacts with steam, iron(II,III) oxide (Fe₃O₄) and hydrogen gas are formed. The balanced chemical equation for this reaction is:
Correct: B
The unbalanced equation is Fe(s) + H₂O(g) → Fe₃O₄(s) + H₂(g).
1. Balance Fe atoms: There are 3 Fe atoms on the right (Fe₃O₄), so place a coefficient of 3 in front of Fe on the left: 3Fe(s) + H₂O(g) → Fe₃O₄(s) + H₂(g).
2. Balance O atoms: There are 4 O atoms on the right (Fe₃O₄), so place a coefficient of 4 in front of H₂O on the left: 3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + H₂(g).
3. Balance H atoms: Now there are 4x2 = 8 H atoms on the left (4H₂O). Place a coefficient of 4 in front of H₂ on the right: 3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g).
The equation is now balanced.